Intake control for multiple piston pump



March 25, 1969 c, |1 3,434,428

INTAKE CONTROL FOR MULTIPLE PISTON PUMP Filed June 5, 1967 Sheet of 4 mrewrae. 4J (bra/ray b/ef March 25, 1969 c. E. LILES 3,434,428

INTAKE CONTROL FOR MULTIPLE PISTON PUMP Filed June 5, 1967 Sheet 2 of4 mnswraz 4 flare/me 61 Z//e.r

% yfkp ds Ta/a/ Lfdl C. E. LILES INTAKE CONTROL FOR MULTIPLE PISTON PUMP4. w x I w w m wmn mm/ DZ 7 w w r e m wdfi/ w fimr an fl 3m W #6 ,7 a? wMarch 25, 1969 Filed June 5, 1967 March 25, 1969 c. E. LILES 3,434,428

INTAKE CONTROL FOR MULTIPLE PISTON PUMP Filed June 5, 1967 Sheet io4Anne/veg:

nited States Fatent U US. Cl. 10340 7 Claims ABSTRACT OF THE DISCLOSUREAn automatic control for a multiple cylinder pump maintainssubstantially constant output pressure by regulating the intake flow inresponse to changes in the output pressure. A small intake port for eachcylinder is used for stable operation of the pump at extremely low ratesand an adjacent larger intake port for each cylinder is usedadditionally for larger output rates. An intake valve has an openingmovement which uncovers the small ports and the large portsprogressively in overlapping sequence with a resultant combined rate offlow which varies with the opening movement of the valve in accord witha curve having a desirable gradually rising toe with the rest of thecurve inclined at a desirably moderate slope.

Background of the invention The invention relates to multiple cylinderpumps including both radial cylinder pumps and axial cylinder pumpswherein an automatic control maintains substantially constant outputpressure by varying the rate of output of the pump in response tovariations in the output pressure. More specifically, the inventionrelates to such a multiple cylinder pump in which the output pressure isregulated by controlling the rate of intake flow to the multiplecylinders. For this purpose a single intake valve simultaneouslycontrols the inflow to the multiple cylinders respectively.

The problem to which the invention is directed is the instability in theoperation of the automatic control that occurs at extremely low levelsof the volumetric output of the pump when the pump is operating at belowten percent of its capacity. A time lag occurs in the rise in pumpoutput in response to changes in the low level demand, which time lagcauses instability of the operation of the control mechanism, thecontrol mechanism overshooting and becoming out of phase with thedelivery of the pump pistons.

By careful investigation it has been discovered that the time lag occursbecause the intake port is so much larger than necessary to accommodateextremely low rates of intake flow and is in addittion to the inherentpiston fill lag time. The nature of the cause of the volume time lag maybe understood when it is considered that the intake port to eachcylinder is periodically uncovered by the corresponding piston only whenthe piston is retracted during one-third of its cycle, the retraction ofthe piston creating a vacuum with the pressure in the cylinder droppingas low as a fraction of a p.s.i.a. When the intake valve is adjusted fora moderately high rate of intake flow, the intake fluid flows freelythrough the cavity into the evacuated cylinder with no troublesome timelag. When the intake valve is adjusted for a very low rate of intakeflow, however, the restricted intake stream expands in the intake portcavity because the abrupt pressure drop and the expansion releases theapproximately 10% of dissolved air content of the hydraulic fluid tocause the hydraulic fluid to froth and behave more like a gas than aliquid. The time required for expansion of the restricted stream offluid in the relatively large intake port cavity results in a time lagof 200 to 300 milliseconds which is suificient to cause the undesirableinstability of the control loop.

Snmmaiy of the invention The invention meets the foregoing problem byproviding a plurality of intake ports for each cylinder with a singlevalve member controlling all of the ports and preferably by also placingthe intake valve close to the cylinders to minimize the axial dimensionsof the intake ports. In the presently preferred embodiment of theinvention there is a pair of intake ports for each cylinder comprising asmall intake port of low intake capacity and a larger intake port.

With progressively increasing demand starting from an extremely lowlevel, the intake valve progressively uncovers the small port and thelarge port for each cylinder in overlapping sequence. Thus when the pumpis operat ing at an extremely low rate in the range of below ten percentof its volumetric capacity, flow into each cylinder is solely throughthe corresponding small intake port and the size of the small intakeport matches the rate of intake flow closely enough to avoid atroublesome degree of fluid expansion. As demand increases withprogressive unmasking of the small port, progressive unmasking of thelarger port is initiated before the smaller port is completelyuncovered. Thus the progressive uncovering of the small port overlapsthe progressive uncovering of the larger port.

The relative flow capacity of the two intake ports and their relativepositions for the overlapping sequence are such that the rise in totalflow with increasing demand is represented by a curve having a desirablyprolonged and graduated toe with the main portion of the curve rising ata desirably moderate slope. During transient conditions when additionalflow through the larger port is required to meet the demand, the smallport provides sulficient intake flow to sustain the output of the pumpand to sustain the pressure signal from the output manifold while thelarger port is being brought up to operating pressure.

In a radial piston pump the intake valve that is common to all of thecylinders is preferably in the form of a rotary valve disk mounted inthe intake manifold of the pump. In an axial piston pump the intakevalve is preferably an axially movable sleeve cooperating with an innercircumferential wall from which the pairs of intake ports radiate to theseveral cylinders.

The features and advantages of the invention may be understood from thefollowing detailed description and the accompanying drawings.

Brief description of the drawings In the drawings, which are to beregarded as merely illustrative:

FIG. 1 is an axial cross section of a radial piston pump embodying theinvention;

FIG. 2 is an elevational view of the intake valve and the pairs ofintake ports that are controlled by the valve;

FIG. 3 is a fragmentary sectional view perpendicular to the axis of oneof the cylinders as seen along the line 33 of FIG. 5 and showing the twointake ports in longitudinal section;

FIG. 4 is a section along the line 4-4 of FIG. 1 and the line 44 of FIG.3, the section being perpendicular to the two intake ports;

FIG. 5 is a fragmentary view like FIG. 2 showing the valve member at adiiferent position;

FIG. 6 is a diagram that illustrates the cycle of operation of a pistonin a cylinder with reference to the opening of the associated pair ofinlet ports;

FIG. 7 shows curves representing the pressure and rate of flow throughthe two intake ports respectively throughout the range of adjustment ofthe intake valve;

FIG. 8 is a view similar to FIG. showing different configurations forthe intake valve and a large intake port;

FIG. 9 is a transverse section of an axial piston pump embodying theinvention with a section broken away to disclose the portingarrangement;

FIG. 10 is a fragmentary view showing the relation of a sleeve-typeintake valve in FIG. 9 to a pair of the intake ports; and

FIG. 11 is a view similar to FIG. 4 showing the relation of a pair ofintake ports to the piston in a cylinder.

Description of the preferred embodiments The first embodiment of theinvention shown in FIGS. 1-5 is a six-cylinder radial piston pumpwherein the discharge end of each of the cylinders is normally closed bya discharge valve 22 under the pressure of a coil spring 24. Thedischarge valve controls communication with a corresponding dischargepassage 25 that leads to a common annular high pressure manifold 26. Thepistons in the various cylinders 20 are actuated by an eccentric 32 on adrive shaft 34 that is journalled in suitable bearings 35, the axis ofthe shaft being the operating axis of the pump. In a well known mannerthe eccentric 32 is embraced by a roller bearing comprising acircumferential series of rollers 36 and an outer race in the form of asleeve 38. In the construction shown the sleeve 38 is equipped with apair of flanged rings 40 which engage circumferential grooves 42 in theinner ends of the pistons to retract the pistons after they are drivenradially outward by the action of the eccentric.

An annular low pressure intake manifold 44 has a planar annular face 45from which pairs of intake ports extend to the respective cylinders 20under the control of a rotary intake valve 46 that presses against theannular face. In a well known manner, a control system for maintainingsubstantially constant pressure in the high pressure manifold 26includes a pressure-sensing means represented diagrammatically by ablock 48 which responds to the pressure in the high pressure manifoldand which controls a hydraulic actuator 50. The hydraulic actuator 50regulates the position of the intake valve 46 by engagement with acontrol pin 52 that extends laterally from the intake valve.

FIGS. 3 and 4 show how each of the cylinders 20 is provided with a smallintake port 54 and an adjacent large intake port 55, the two intakeports being in the form of bores that open to the annular face 45 of theintake manifold 44. It is to be noted that when a piston 30 retractsfrom the corresponding discharge valve 22 the piston initiatesuncovering of the two intake ports 54 and 55 simultaneously as may beseen in FIG. 4. The diagram in FIG. 6 shows the piston cycle and showshow the two inlet ports communicate with a cylinder during one-third ofthe piston cycle when the piston is retracted from the correspondingdischarge valve.

As may be seen in FIG. 2, the rotary intake valve 46 has acircumferential series of peripheral masking portions 56 separted bygaps 58 for cooperation with the various pairs of intake ports 54 and55. FIG. 2 shows the position of the intake valve 46 relative to thepairs of intake ports 54 and 55. In FIG. 2 the intake valve 46 isadjusted for a moderately high rate of intake flow with all of the smallintake ports 54 at the gaps 58 and with each of the large intake ports55 partially covered by a masking portion 58 of the valve.

FIG. 5 shows the position of the intake valve 46 for an exceedingly lowrate of intake flow, each of the small intake ports 54 being partiallycovered by a masking portion 56 of the valve member and each of thelarger intake ports 55 being completely covered by a masking portion. Itis apparent from FIGS. 2 and 5 that when the intake valve 46progressively rotates counterclockwise from a completely closed positionit first initiates uncovering of the small intake ports 54 and thenbefore the small intake ports are completely uncovered the intake valveinitiates uncovering of the larger intake ports 55.

Referring now to FIG. 7 the curve 60 shows the delayed rise of pressurein a large intake port 55 that accounts for the troublesome time delaythat would occur if solely the large intake port was relied upon forintake flow at an extremely low flow level. The curve 62 shows theabrupt rise of pressure in a small intake port 54 that eliminates thetime lag that is inherent in the functioning of the larger intake port.

The curve 64 shows the delayed rise in rate of fiow through a largeintake port 55 as the intake valve is moved progressively fromcompletely closed position towards fully open position, the curveshowing how initiation of flow through the large intake port is delayedby the delayed uncovering of the large port. Curve 65 in FIG. 7 showshow the flow through a small intake port 54 is initiated as soon as thevalve moves out of its completely closed position and shows how the flowinitially rises at a desirably graduated rate. Curve 66 shows the resultor combined flow through the two intake ports, the curve being ideal forthe purpose of the invention since the curve has a prolonged graduatedtoe 68 with the rest of the curve at a moderate slope.

FIG. 8 shows different configurations that may be employed for theintake valve and the larger intake port of each pair of intake ports. InFIG. 8 the small intake port 54a is of the usual circularcross-sectional configuration at the planar face of the intake manifoldbut the larger intake port 55a is tapered in cross section as shown withthe tapered portion in overlapping relation to the smaller intake port.The rotary intake valve 46a in FIG. 8 is shaped and dimensioned toinitiate uncovering of the small intake port 54a and then before thesmall intake port is completely uncovered the intake valve initiatesuncovering of the tapered portion of the larger intake port 55a. Thusthe arrangement shown in FIG. 8 functions in the same general manner asthe arrangement shown in FIGS. 2 and 5.

FIGS. 911 show how the basic concept of the invention may be embodied inan axial piston pump, generally designated 70, that has acircumferential series of cylinders 72 that are parallel to and equallyspaced from an operating axis represented by the dot 74. The pump has aconcentric low pressure intake manifold 75 that has a cylindrical innercircumferential surface 76 with pairs of intake ports comprising smallintake ports 54]) and large intake ports 55b extending from thecylindrical surface to the various cylinders 72. Each of the largerintake ports 55b includes a crescent shaped recess 78 in the Wall of thecorresponding cylinder. FIG. 11 shows the positions of the two intakeports 54!) and 55b relative to the corresponding piston 80 in each ofthe cylinders 72.

All of the pairs of intake ports 54b and 55b are controlledsimultaneously by an intake valve 84 in the form of an axially slidablesleeve that fits snugly against the inner circumferential wall 76 of theintake manifold. FIG. 10 shows the relation of a pair of the intakeports 54b and 55b to the intake valve 84 and shows how the rim of theintake valve may be formed with a semi-circular recess 85 to cooperatewith each of the small intake ports 54b. It is apparent in FIG. 10 thatretraction of the intake valve 84 towards its fully open position firstinitiates uncovering of a small intake port 5412 by the correspondingrecess 85 of the valve and then before the small intake port iscompletely uncovered the valve initiates uncovering of the larger intakeport 55b. Thus the intake valve 84 regulates the intake flow in the samegeneral manner as in the first described embodiment of the invention.

I claim:

1. In a multiple cylinder pump wherein the intake ports of therespective cylinders are controlled by an intake valve for control ofthe output pressure and a control system regulates the intake valve inresponse to changes in the output pressure, the improvement to minimizeinstability in the operation of the control system at low flowadjustments of the intake valve, comprising:

each of the cylinders having a pair of intake ports comprising arelatively small intake port and a separate larger intake port, saidsmall intake port being positioned relative to the intake valve to beprogressively opened thereby as intake flow is increased fromsubstantially zero,

said large intake port being positioned relative to the intake valve tobe progressively opened and to be initially opened subsequent to theinitial opening of the small intake port as the intake flow isincreased, the progressive opening of the two ports overlapping toresult in smoothly increasing total flow through the two ports with nosubstantial time lag between a drop in the output pressure of the pumpand the consequent opening movement of the intake valve when the pumpoutput is at a low level.

2. An improvement as set forth in claim 1 in which the axes of themultiple cylinders are arranged radially of an operating axis and thecorresponding multiple pairs of intake ports open onto a planar surfacethat is parallel to the cylinders with the pairs of intake portsarranged in a circle on said surface,

and in which said intake valve is rotatable about the operating axis inabutment with said surface and has circumferentially spaced maskingportions to control flow into the pairs of intake ports,

each of said masking portions having an edge positioned to unmask asubstantial portion of the corresponding small intake port beforeunmasking the corresponding large intake port.

3. An improvement as set forth in claim 1 in which the axes of themultiple cylinders are parallel and equally spaced from an operatingaxis,

in which the corresponding multiple pairs of intake ports open onto acylindrical surface concentric to the operating axis,

and in which said valve means is a sleeve axially movable along thecylindrical surface with an edge portion of the sleeve positioned tocooperate with each of the pairs of intake ports,

each of said edge portions being shaped and positioned to unmask asubstantial portion of the corresponding small intake port beforeunmasking the corresponding large intake port.

4. An improvement as set forth in claim 1 in which said ports of each ofsaid pairs of ports are dimensioned and located relative to thecorresponding masking portion of the intake valve for a total flow whichvaries with the opening movement of the intake valve in accord with acurve having a toe portion of low inclination and a main portion ofgreater but moderate inclination.

5. An improvement as set forth in claim 4 in which the flow through eachof the large intake ports varies with the opening movement of the intakevalve in accord with a curve having a main portion of approximately theinclination of said main portion of the first mentioned curve and theflow through each of the small intake ports varies with opening movementof the intake valve in accord with a curve that has a relatively longtoe and rises to a relatively low plateau.

6. In a pump having a radial array of cylinders with pistons therein,said pump having an arcuate intake manifold and a control system whichregulates the rate of output of the pump by varying the rate of the pumpintake in response to changes in the output pressure, the improvement topromote stability in the operation of the control system at low outputrates, comprising:

said intake manifold having a planar face on the side thereof adjacentthe cylinders,

pairs of intake ports extending from said face to said cylindersrespectively,

one intake port of each pair being of relatively small cross section toprovide intake flow at the lower end of the range of pump output, theother port of each pair being of relatively large cross section toprovide additional intake flow at higher rates of pump output; and

a rotary valve member regulated by said control systern, said valvemember being in abutment with said planar surface and having maskingportions corresponding to the respective cylinders,

each of said masking portions being shaped and dimensioned to uncoverthe corresponding small intake port and large intake port progressivelyin overlapping sequence.

7. In a pump having multiple cylinders, the axis of which are paralleland equally spaced from a central axis, said pump having an intakemanifold and a control system which regulates the rate of output of thepump by varying the rate of pump intake in response to changes in theoutput pressure, the improvement to promote stability in the operationof the control system at low output rates, comprising:

said intake manifold having an inner circumferential cylindrical surfaceconcentric to said central axis, pairs of intake ports extending fromsaid cylindrical surface to said cylinders respectively, one intake portof each pair being of relatively small cross section to provide intakeflow at the lower end of the range of pump output, the other port ofeach pair being of relatively large cross section to provide additionalintake flow at higher rates of pump output, and a cylindrical valvemember movable axially along said cylindrical surface and regulated bysaid control system with portions of the valve member positioned to maskand unmask the pairs of ports respectively,

each of said masking portions being shaped and dimensioned to uncoverthe corresponding small intake port and large intake port progressivelyin overlapping sequence.

References Cited UNITED STATES PATENTS 2,433,220 12/ 1947 Huber.2,677,326 5/ 1954 Schindele. 3,050,004 8/ 1962 Heintzmann. 3,151,56910/1964 Muller.

FOREIGN PATENTS 475,311 6/ 1946 Canada. 808,811 10/1935 France.

WILLIAM L. FREEH, Primary Examiner.

US Cl. X.R. 103-174

